Bill Gates

2013 Net Worth: $72 billionBill Gates remains atop The Forbes 400, a perch he's held since 1994, despite giving away $28 billion, most of it to the Bill & Melinda Gates Foundation. He's also again the world's richest person, having reclaimed that title from Mexico's Carlos Slim earlier this year. Shares of Microsoft jumped in late August on news that Steve Ballmer will step down as CEO, but Gates will remain chairman of the software company he cofounded in 1975 with Paul Allen. His stake in Microsoft represents less than a fifth of his fortune.